This invention relates to high temperature resistant epoxy resins for producing hollow fiber membrane modules for high temperature gas separation applications. This invention also relates to a hollow fiber membrane module comprising a high temperature resistant cured epoxy resin tube sheet.
In the past 30-35 years, the state of the art of polymer membrane-based gas separation processes has evolved rapidly. Membrane-based technologies have advantages of both low capital cost and high-energy efficiency compared to conventional separation methods. Membrane gas separation is of special interest to petroleum producers and refiners, chemical companies, and industrial gas suppliers. Several applications of membrane gas separation have achieved commercial success, including N2 enrichment from air, carbon dioxide removal from natural gas and from enhanced oil recovery, and also in hydrogen removal from nitrogen, methane, and argon in ammonia purge gas streams. For example, UOP's Separex™ polymeric membrane is currently an international market leader for carbon dioxide removal from natural gas.
The polymeric membranes most commonly used in commercial gas separation applications are flat sheet or hollow fiber membranes that can be fabricated into spiral wound or hollow fiber membrane modules. The flat sheet or hollow fiber membranes have a thin nonporous selective skin layer that performs the separation and a highly porous non-selective mechanical support layer. Separation is based on a solution-diffusion mechanism. This mechanism involves molecular-scale interactions of the permeating gas with the membrane polymer. The mechanism assumes that in a membrane having two opposing surfaces, each component is sorbed by the membrane at one surface, transported by a gas concentration gradient, and desorbed at the opposing surface. Each spiral wound or hollow fiber membrane module comprises multiple flat sheet or hollow fiber membranes bound together with a cured epoxy resin that is essentially impermeable to the gas pairs to be separated.
UOP Separex™ commercial spiral wound membranes for natural gas upgrading comprise flat sheet membranes made by a phase inversion technique. The Separex™ spiral wound membrane module has the key features of cross-flow, high pressure tolerance, high fouling resistance, high reliability, and ease of installation into space-efficient, skid-mounted units. Some commercial gas separation membranes have hollow fiber configuration and are formed into hollow fiber modules. Hollow fiber membrane modules with much higher membrane area packing density than spiral wound modules have been commercially used for both low pressure and high pressure applications. The key features of hollow fiber modules for high pressure gas separations such as CO2/CH4 separation and H2 purification include cross-flow and good feed flow distribution. The key features of hollow fiber modules for low pressure gas separations, such as On Board Inert Gas Generating Systems (OBIGGS) application and dehydration of air include counter-flow and low fouling.
The state-of-the-art hollow fiber membrane spinning processes allow multiple parallel spinning lines for high throughput, low cost fabrication. The hollow fiber membrane module having a feed gas inlet, a residue outlet, and a permeate outlet comprises a bundle of hollow fiber membranes, wherein one end or both ends of the membrane bundle is fixed and bound together in what is commonly referred to as a tube sheet formed of a cured epoxy resin. The tube sheet is impermeable to the gases and fixes and holds the hollow fibers in a gas-tight relationship. The tube sheet seals between the hollow fibers and between the fibers and the module shell, so that the permeate flow is separated from the feed and residue flows. The hollow fiber membrane modules will lose the separation property if the cured epoxy resin of the tube sheet cracks or decomposes.
Hollow fiber membrane modules have been commercially used for the separation of clean gas streams such as separation of nitrogen or water from air and purification of hydrogen from ammonia purge gas or syngas. However, most of the hollow fiber membrane modules for gas separation applications cannot be operated at temperatures above 80° C. due to the use of the tube sheet formed from low temperature stable cured epoxy resin and the use of low temperature stable packaging material. The low temperature stable cured epoxy resin is typically formed from a low temperature stable epoxy resin and a low temperature stable aliphatic diamine with the advantages of low cost, low viscosity, easy to mix, fast reaction, and room temperature-curing. However, this type of cured epoxy resin with cured network can work up to 80° C., but not above.
Zaki et al. (U.S. Pat. No. 7,867,319) disclosed a filled epoxy tubesheet comprises an epoxy filled with a metal.
Yamaoka et al. (U.S. Pat. No. 8,388,733) disclosed an epoxy resin composition for producing hollow fiber membrane elements that can be operated above 80° C.
It is desirable to develop high temperature resistant epoxy resin for producing hollow fiber membrane modules that can be operated above 100° C. for gas separation applications such as for H2 purifications.